Cushioned bumper for scrapers

ABSTRACT

A cushioned bumper for ground scrapers comprising a housing adapted to be mounted on the rear end of the scraper in a generally horizontal position and extending longitudinally of the scraper, a tubular plunger structure reciprocably mounted in the housing and carrying a buffer plate exposed exteriorly of the housing against which the blade of a bulldozer or the like will engage to push the scraper when stuck, and a composite cushioning arrangement interposed between the housing and the plunger including a pressure responsive variable orifice type hydraulic cushioning unit and one or more resilient pad type cushioning units for cushioning the forces applied to the scraper by the bulldozer.

United States Patent 1191 Peterson et a1.

[ Jan. 15, 1974 CUSHIONED BUMPER FOR SCRAPERS [75] Inventors: Berti] E. Peterson, South Holland; 'r sheridan Richard Housman, Dolton both Assistant Examzner--Robert Sa1fer of L Attorney-Robert C. Brown, Jr. et a1.

[73] Assignee: Cardwell Westinghouse Company, [57] ABSTR CT Chlcago A cushioned bumper for ground scrapers comprising a [22] Filed: Apr. 10, 1972 housing adapted to be mounted on the rear end of the scraper in a generally horizontal position and extend- [211 App! 242329 ing longitudinally of the scraper, a tubular plunger structure reciprocably mounted in the housing and [52] US. Cl 280/481, 293/60, 267/140 rrying a tler plate exposed exteriorly of the hous- [51] Int. Cl. B601- 19/08, ligigjlgg g g in hi h blade f a l oz r r h like [58] Field of Search 280/481; 293/DIG. 1, ill engage to push the scraper when u and a 293/DIG. 2, DIG, 5, 60, 85, 86, 88; 267/22, composite cushioning arrangement interposed be- 33, 35, 116, 140; 213/45, 223, 22, 43; 188/322 tween the housing and the plunger including a pressure responsive variable orifice type hydraulic cush- [56] Refer ce Cit d ioning unit and one or more resilient pad type cush- UNITED STATES PATENTS ioning units for cushioning the forces applied to the 3,214,192 10/1965 Hamm 280/481 scraper by the bulldozer 3,140,080 7/1964 Rumsey 213 22 7 Claims, 6 Drawing Figures FM'I'lElill-JIPL 9O 3O 34 224 W7i1/AMII/II/llgW/I/A 68 36 sm 1 1 1 4' 216 K \1\ \2\\ o1\1\ I 1' l 114 .212 210 B2 40 I O 1 S I g w 1 "2.: i 1 2s lJuLi 1 L- 44 v PATENTED 1 3.785.679 sum 1 M2] FORCE 1N POUNDS TRAVEL IN INCHES PATENTED I 5 4 SHEET 2 [IF 2 1 CUSHIONED BUMPER FOR SCRAPERS This invention relates to a cushioned bumper for scrapers, and more particularly, to a cushioned scraper bumper adapted for application to the rear end of earth moving scrapers to cushion the shock involved when the scraper is bumped from the rear to start it when stuck.

Scrapers are familiar pieces of earth moving equipment which take on a load by moving the scraper over earth to be moved, with the scraping blade lowered to take on the load of earth, and when loaded, the scraper is moved to another location where the scraper is discharged in a conventional manner. Scrapers being large and heavy pieces of equipment, and being used primar' ily to handle relatively soft earth, they frequently become stuck during the process of being loaded and moved to the point of earth disposal. As equipment of this type may weigh on the order of 50,000 pounds, and carry a 50,000 pound load, it is quite a problem to get them started moving once they have stalled.

The practice has developed in the industry of using a bulldozer to get a stuck or mired scraper moving, and this is accomplished by moving the bulldozer against the rear end of the scraper (which is equipped with a fixed bumper for that purpose) so that the power provided by the scraper can be applied to the scraper to get the scraper moving. Of course, it would be preferable to be able to run the bulldozer against the rear end of the scraper at low but controlled speed, but the resulting impact would create quite a whiplash problem for the operators, and overstress the equipment involved. Operators for their own safety have come to require that the bulldozer start up from a full stop, after the bulldozer blade is carefully brought against the scraper bumper, to minimize the whiplash problem. This, of course, wastes time and requires a lot more power and fuel than if the bulldozer could run into the scraper bumper while moving.

A principal object of this invention is to provide ,a cushioned scraper bumper which permits the bulldozer to impact the scraper at speeds of one to two miles per hour without subjecting the operators to whiplash effects, or overstressing the equipment.

Another principal object of the invention is to provide a cushioned bumper arrangement for scrapers which accommodates the impacting of the scraper against immovable obstructions such as boulders or the like without overstressing the cushioning device or the scraper and bulldozer equipment involved.

Other objects of the invention are to provide a cushioned scraper bumper arrangement that employs a hydraulic cushioning action throughout the bumper closure stroke, which is supplemented in the latter portion of the stroke by resilient cushioning for maximum energy absorbing purposes, that is arranged to avoid clogging in spite of the fouling conditions under which such equipment usually work, that is economical of manufacture, convenient to install, and long lived in operation.

In accordance with this invention, a cushioned scraper bumper is provided comprising a housing adapted to be mounted on the rear end of the scraper in a generally horizontal position and extending longitudinally of the scraper, a tubular plunger structure reciprocably mounted in the housing and carrying a bumper plate exposed exteriorly of the housing against which the plate of a bulldozer or the like impacts to push the scraper when stalled, and a composite cushioning arrangement interposed between the housing and the plunger including a pressure responsive variable orifice type hydraulic cushioning unit and one or more resilient pad type cushioning units that absorb the impetus of the dynamic forces applied to the scraper by the bulldozer. The hydraulic cushioning unit provides a hydraulic cushioning action for the full stroke of the unit in a manner which allows for the scraper engaging against fixed obstructions such as boulders or the like, with the resilient cushioning units coming into operation at approximately the three-quarter point of the closure stroke to act in parallel with the hydraulic unit in absorbing the impetus of the pushing forces involved. The result is that the scraper when stalled can be pushed into motion when fully loaded by impacting the bulldozer into the scraper at speeds on the order of one to two miles per hour while not exposing the vehicle operators to whiplash problems or overstressing the equipment. Similarly, if the scraper in being pushed strikes immovable objects such as boulders or the like, the hydraulic cushioning device acts to fully cusuion the resulting shock without overstressing the cushioning mechanism or the vehicles and without causing distress to the operator.

Still other objects, uses, and advantages will be obvious or become apparent from a consideration of the following detailed description and the application drawings.

In the drawings:

FIG. 1 is a diagrammatic perspective view of the rear end of a typical scraper, showing a cushioned bumper applied thereto that is in accordance with the present invention;

FIG. 2 is a graph illustrating the manner in which the cushioning device acts, in accordance with this invention, in absorbing dynamic forces applied to the cushioning device to start a stalled scraper;

FIG. 3 is a side elevational view of the scraper bumper, with parts broken away;

FIG. 4 is a plan view of the cushioning device shown in FIG. 3, with parts shown in section;

FIG. 5 is an end view of the device shown in FIG. 4, taken from the right hand side of FIG. 4; and

FIG. 6 is an enlarged fragmental view illustrating a detail of the hydraulic cushioning device.

However, it is to be understood that the specific drawing illustrations provided are supplied primarily to comply with requirements of the Patent Laws, and that the invention is susceptible of other embodiments that will be obvious to those skilled in the art, and which are intended to be covered by the appended claims.

GENERAL DESCRIPTION Reference numeral 10 of FIG. 1 generally indicates a cushioned scraper bumper arranged in accordance with this invention applied to the rear end 12 of an earth moving scraper 14 for purposes of starting the scraper 14 when stalled by using a bulldozer or the like piece of equipment. The scraper 14 is not shown except for its rear end 12, and it may be any one of a number of conventional makes well known to the art. Examples are the B339F tractor scraper made by The Construction Equipment Division of Westinghouse Air Brake Company and the TS-24 Terex scraper made by the Terex Earth Moving Equipment Division of General Motors Corporation. In any event, the scraper 14 comprises a suitable frame 16 which typically terminates in a rearwardly extending projection 18 which forms the rear end 12 of the scraper 14, to which the usual fixed bumper plate (not shown) is suitably applied.

The cushioned bumper 10 generally comprises a housing 20 having a base plate 22 closing one end 24 of same, with the other end 26 being open as at 28 to receive a plunger structure 30 which has one end 32 of same directed towards the base plate 22 and the other end 34 equipped with a suitable bumper plate structure 36.

Interposed between the plunger structure 30 and the housing 20 is hydraulic cushioning unit 40 (see FIGS. 4 and 6) which is of the pressure sensitive variable orifice metering type, and, in the embodiment illustrated, a pair of resilient cushions 42 disposed on either side of the hydraulic cushioning unit.

The end 32 of the plunger structure 30 seats against the base plate 22 to define the fully contracted relation of the bumper, and the plunger structure 30 carries on either side of same a lug 44, which lugs 44 respectively cooperate with the special built up lug plates 46 applied to either side of the housing to define the extended relation of the bumper, under the biasing action of return springs 48 and 50.

In accordance with this invention, a scraper 14 that is stalled is brought into movement by a bulldozer impacting into the bumper plate 36 of the cushion bumper 10 at a speed on the order of l to 2 miles per hour, with the bumper following the reaction curve 52 that is generally similated in FIG. 2 of the drawings. As indicated in FIG. 2, the force travel involved is initially substantially horizontally, and thus is substantially of the constant force travel, and then slowly rises to about the l0,000 lb. reaction force level at approximately the three-quarter point of the stroke length, at which point the reaction force smoothly curves upwardly to about the 80,000 lb. level at the end of the stroke.

In this connection, as indicated at 54 in FIG. 2, the hydraulic cushioning device 40 allows a safety factor, represented by the bulge in the curve 52 which is indicated by the dashed line 54, in the event that the scraper when being pushed by the bulldozer through the bumper l strikes an immovable object such as a boulder. After the initial shock of striking such an object is passed, the reaction force curve returns substantially to its design level for completion of the cushioning stroke.

The overall result is that neither the equipment or the operators are subjected to undue impact shocks even though the bulldozer can run into the bumper at speeds on the order of one to two miles per hour to get the stalled scraper into motion.

SPECIFIC DESCRIPTION The housing 20 in addition to base plate 22 generally comprises top and bottom plates 60 and 62 and side plates 64, fixed together as by welding, to define a guideway 68, of generally quadrilateral transverse cross-sectional configuration (rectangular in the illustrated embodiment, see FIG. for the plunger structure 30, which is similarly contoured. The base plate 22 is fixed, in the illustrated embodiment, to the standard fixed buffer mounting plate 70 (see FIG. 4) that forms a part of the scraper frame 16, as by employing suitable bolts 72.

Side walls 64 are each formed with a slot 74, extending longitudinally of the housing side wall 64, and from their forward edges 76, in which the respective lugs 44 of the plunger structure operate.

Applied over each slot 74, as by employing suitable bolts 78, is the lug plate 46 having fixed to the forward edge 82 of same, along the inside surface 84 of the respective plates 46, a lug structure 86 with which the lugs 44 respectively cooperate with (see FIG. 4). The lug structure 86 in the form shown comprises a plate 90 having its center open as at 92 (see FIG. 3) about which the plate 90 is welded to the plate 46 where indicated at 94. The plate 90 is also welded to plate 46 as at 96, at the front edge 82 of the plate 46.

As indicated in FIGS. 3 and 4, the side edge 98 of the lugs 44 respectively engage the side edge 100 of the respective lug forming plates 90, under the biasing action of return springs 48 and 50.

The housing bottom plate is notched, as indicated at 101 in FIGS. 3 and 4, for self cleaning purposes, as hereinafter indicated. Lug plates 46 are each formed with vent openings 103 for a similar purpose.

Reinforcing webs 106 are suitably affixed between the laterally extending ends 108 of the base plate 22 and the respective plates 64, as by welding, and above and below the slots 74. Fixed across top plate 60 is brace plate 109 that provides reinforcement necessary when the bulldozer lifts up on the outer end of the plunger when pushing.

The plunger structure 30 comprises in the form shown a hardened bumper plate structure 36 affixed by welding to top and bottom plate 112 and 114 and side plates 116. Plate structure 36 in the form shown comprises a segmental arrangement in the form of top and bottom segments and 122, side segments 124 and 126 and middle segment 128 formed from a suitable hardened steel and fixed together as by welding. The contact face defined by plate structure 36 is such that the buffer plate structure 36 presents the generally frusto-pyramididic contour indicated in the drawings, to avoid presenting right angled corners for engagement by the bulldozer blade.

The lugs 44 each comprise a metal block 132 suitably affixed to the respective plunger structure side plates 116, as by welding at 134.

The hydraulic cushioning unit 40 is of the general type shown in Campbell and Natschke Reissue US. Pat. No. 27,159 and Cardwell US. Pat. No. 3,368,698, to which reference may be had for more specific details of the cushioning device. In the form shown, the cushioning unit 40 comprises ram having one end 142 studded as at 144 for reception in end plate 146 (which seats against plunger front plate 36), and having its other end 148 formed as indicated in FIG. 6 for application within hydraulic cylinder 150.

Cylinder 150 at its end 152 seats against the housing structure base wall 22, and at its other end 154 is equipped with an annular cylinder head member 156 through which ram 140 extends, and to which is suitably secured one end 158 of a flexible boot 160 which has its other end 162 suitably secured to the ram 140, as in the manner described in said patents, whereby the boot 160 forms a non-sliding or static (as distinguished from sliding or dynamic) seal between the cylinder head 156 and the ram.

As indicated in FIGS. 4 and 6, the end 148 of the ram 140 defines a ram or piston head 166 equipped with a suitable seal 168 suitably employed between the ram head and internal surface 170 of the hydraulic cylinder 150.

The ram head 166 is further formed to define a chamber 172 in which is mounted a valve member 174 including a head 176, ported as at 177, and a guiding stem 178, with the chamber 172 also receiving a compression spring 180 that biases the valve head 176 against cross pin 182.

The valve head 174 has its rim 184 in substantial complemental relation to counterbore 186 of chamber 172, with the stem 178 moving in guideway 188 that is formed in the ram head, which is connected by a bore 190 to the space enclosed by the boot 160, the cylinder head 156, and the ram head 166 and cylinder surface 170.

The ram head 166 is formed with a plurality of passages 192 obliquely through the side wall of the ram head which connect the high pressure chamber 194, that is defined by the ram head and hydraulic cylinder 150, with the low pressure chamber 196 that is defined by the hydraulic cylinder as ram head 156, and boot 160. The passages 192 are equally spaced about the rim of the ram head, and may be of any suitable number, although only one passage 192 is shown.

Return spring 50 is received about the ram 140 and boot 160, and is interposed between the ram end plate 146 and the end 154 of the hydraulic cylinder 150. Return spring 48 is received in concentric relation about the spring 50, and between the plunger structure front plate 36, and base plate 22.

The spring 48 that seats against the front plate 36 is received between a pair of centering plates 202 (see FIG. 3) that are suitably affixed to the top and bottom plates of the plunger structure 30, and between a pair of centering structures 204 disposed at right angles with respect to the plates 202, each comprising an upstanding guide plate 206 suitably reinforced by strengthening web 208, with the plates 206 and 208 being suitably affixed to the plunger plate 36, as by welding. Thus, the centering plates 202 and 206 alternate at right angled positions about the circumference of spring 48.

The resilient spring devices 42 each comprise a tubular stud 210 suitably fixed to the housing base plate 22, as by welding, and receiving over same annular pad 212 and an impact plate 216 that is also annular in nature. The pad 212 may be formed from butyl rubber, a suitable polyurethane, or the like, and is intended to be of resiliently compressible material that compresses in rubber spring-like manner on being stressed, and which restores itself to its original configuration on being released.

Each resilient spring device 42 further includes a pressure plate 218 that is fixed to the plunger structure top, bottom and side plates, as by welding, and is formed with central opening 220 that receives the tubular stud 210, as indicated in FIG. 4.

In the form shown, the plunger structure 30 has a travel stroke extending from the extended position of FIG. 4 to a retracted position in which the end 226 of the plunger structure engages the surface 224 of base plate 22 though this only occurs in practice wherein extremely heavy long duration impacts are occasioned. In one successful embodiment of the invention, this stroke is four and threequarter inches, with the hydraulic cushion 40 having a stroke of three and one-half inches prior to the engagement of the impact plates 218 with the pad plates 216, after which the resilient cushions 42 act in parallel with the hydraulic cushion to complete the cushioning stroke. The resilient cushions 42 are designed to preclude metal to metal contact within the bumper.

The hydraulic cushioning unit 40 is of the pressure sensitive variable orifice type described in said patents that provides the desired cushioned bumper closure reaction characteristic without required programmed metering of the type that is involved in cushioning devices having tapered pins, grooves and the like for metering fluid flow. The metering orifice control of this device is regulated by instantaneous pressures on the high pressure side of the ram head (or piston), with the valve head 176 retracting to the right of FIG. 6 with respect to the ram head as an impact is applied to the plunger structures 30 to permit hydraulic liquid on the high pressure side of the ram head 166 to flow to the low pressure side thereof through the passages 192. As the plunger structure 30 retracts under an impact, ram head 166 moves toward base plate 22, and boot fills with the hydraulic liquid that is displaced by the entry of the ram into the hydraulic cylinder. The pressure sensitive orifice arrangement that is involved in unit 40 involves a relation of areas of the valve member 174 exposed to the high pressure liquid, the strength of spring and the effecting areas of ports 192 through which the high pressure liquid discharges to achieve the force travel characteristic that is desired for the hydraulic cushion, based on the masses and impact speeds under consideration.

After the impact has been dissipated, the components of the hydraulic unit return to the position of FIG. 4 under the biasing action of springs 48 and 50, with the hydraulic liquid returning to the chamber 194 through the orifices 177 of valve head 176, and the leakage between the seal ring 168 and the cylinder internal surface 170.

The scraper bumper 10 preferably operates in the manner indicated by FIG. 2, based on our experience in working with this problem. It is preferred that the bumper provide no more than about 2,000 lbs. of initial reaction force due to coil springs along to take care of the very low velocity approaches of the bulldozer, i.e., O to V2 m.p.h., and that for impacts over one-half mph the force travel curve for the combined unit be initially relatively flat but slowing rising to about the 10,000 lb. level at the point where the resilient springs 42 come into operation, whereupon the curve for composite operation rises to about the 80,000 lbs. reaction force level at the end of the plunger structure stroke. The design of the valve spring 180 and associated parts is in accordance with these criteria, thus permitting a bulldozer to impact against the bumper 10 at a speed of one to two miles per hour to get the scraper moving without inflicting shock forces and distress to machinery and personnel.

In the form shown, suitable reinforcing plates 250 are fixed between the upper and lower housing plates and the scraper frame 16. The plates 250 are formed with openings 252 to receive chains applied to a jack device of a suitable type, for securing the respective upper plates 250 to the respective lower plates 250, across the buffer plate 36, with the jack device seated against plate structure 36, whereby compression of the plunger structure inwardly of the housing may be effected against the action of biasing springs 48 and 50 for purposes of disconnecting the plates 46 from housing side plates 64 to disassemble the bumper.

As indicated, the scraper 10 is employed by suitably applying it to the rear end of a scraper frame, in the manner indicated, and when the scraper is stuck, a bulldozer is moved up against the bumper, with an impact speed of one to two miles per hour. Continued movement of the bulldozer against the scraper bumper applies pushing movement to the scraper through the bumper, with the bumper contracting to cushion the impetus of the pushing action involved, following the general force travel curve illustrated in FIG. 2. In the event that the scraper, while being pushed by the bulldozer, encounters an immovable obstruction, such as a boulder, the hydraulic cushioning unit immediately acts to absorb the shock involved, which is accomplished by compression of the valve spring 180 under the additional pressures generated in the high pressure chamber of the hydraulic unit. If the scraper movement ceases momentarily due to the obstruction, and then moves on, the cushioning involved provides for the peaks illustrated by the dashed lines 54 of FIG. 2, with the force travel curve returning to the prescribed level of force after the obstruction has been passed. If the scraper does not move further, the scraper bumper completes its travel, thus protecting both equipment and operators from undue shock due to the impact against the obstruction.

As the plunger structure 30 moves inwardly of the housing 20 under impact, extraneous matter that tends to enter between the plunger and the housing walls vents outwardly of venting openings 101 and 103, thus providing a self cleaning action.

Ordinarily, it is the lower side of the bumper plate structure 36 that is engaged by the bulldozer blade, and the upper side of same can be brought into use by removing the plunger structure and turning it upside down, and then reapplying same. The relation of the plunger structure and housing, as well as the manner of fixing the housing to the scraper frame, permits the bulldozer blade to apply a lifting action on the bumper, as well as a pushing action.

The foregoing description and the drawings are given merely to explain and illustrate the invention and the invention is not to be limited thereto, except insofar as the appended claims are so limited, since those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

We claim:

1. A cushioned bumper for scrapers, said bumper comprising:

a housing having a base wall at one end of same and having its opposite end open,

a tubular plunger structure reciprocably mounted in said housing for movement toward and away from said base wall for a stroke of predetermined length,

said base wall being normal to the path of movement of said plunger structure,

said plunger structure projection exteriorly of said housing through said open end of said housing and carrying a buffer plate on the projecting end thereof closing said projecting end of same,

composite cushioning means operatively interposed between said plunger structure and said base wall for cushioning the impetus of impacts applied to said plunger acting longitudinally of the path of movement thereof,

said cushioning means comprising:

a hydraulic cushioning unit operatively interposed between said plunger structure and said base wall for hydraulically cushioning said impacts throughout said stroke length in moving from an extended to a contracted relation,

said hydraulic unit being of the pressure sensitive orifice metering type and being received within said housing and said plunger structure,

and one or more resilient cushioning units applied to said base wall in the path of movement of said plunger structure,

a pad of resiliently compressible material mounted in said housing against abutment means made fast to said housing,

said plunger structure including an abutment member made fast thereto positioned to move toward and away from said resilient cushioning unit as said plunger structure moves along its path of movement and positioned to engage said pad after a predetermined movement of said plunger structure under an impact toward said base wall,

means for making said housing base wall fast to the scraper,

and means for biasing said plunger structure outwardly of said housing to return said hydraulic cushioning unit to its extended relation,

said housing and said plunger structure being of generally complemental quadrilateral cross-sectional configuration defining opposed side walls on either side of same,

with the plunger structure side walls each including a stop lug on the outwardly facing side of same,

said housing side walls being respectively slotted longitudinally of said path of movement to receive the respective plunger structure lugs,

said housing side walls each having made fast thereto over their said slots a mounting plate including a stop lug disposed in the path of movement of the respective plunger structure lugs to limit movement of said plunger structure outwardly of said housing and define one end of said stroke.

2. The cushioned bumper set forth in claim 1 wherein:

said mounting plates are formed with a venting perforation in alignment with the lower edge of each said slots and adjacent either end of said slots,

whereby extraneous material accumulating in said slots is discharged through said venting perforations on cushioning operation of said bumper.

3. The cushioned bumper set forth in claim 1 wherein:

said housing adjacent the base of said base wall is formed with spaced venting perforations,

whereby extraneous material accumulating within said housing is discharged through said venting perforations.

4. The cushioned bumper set forth in claim 1 wherein:

said plunger structure engages said base wall to limit movement of said plunger structure inwardly of said housing and defines the other end of said stroke.

5. The cushioned bumper set forth in claim I wherein said resilient cushioning units further each comprise:

said pad of said resilient cushioning units being annular in configuration,

said pad being received on a centering stem made fast to said base wall and extending toward said plunger structure,

said pad being seated against said base wall on one side of said pad,

and including an annular abutment member on the other side of said pad against which said plunger structure abutment member engages to compress said pad.

6. The cushioned bumper set forth in claim 1 wherein:

said housing and said plunger structure are rectangular in transverse cross-sectional configuration,

and wherein said resilient cushioning unit and said plunger structure are in duplicate form on either side of said hydraulic cushioning unit,

said hydraulic unit being self contained in nature.

7. A cushioned bumper for scrapers, said bumper comprising:

a housing having a base wall structure at one end of same and having its opposite end open,

a tubular plunger structure reciprocably mounted in said housing for movement toward and away from said base wall for a stroke of predetermined length,

said base wall being normal to the path of movement of said plunger structure,

said plunger structure projecting exteriorly of said housing through said open end of said housing and carrying a buffer plate on the projecting end thereof closing said projecting end of same,

composite cushioning means operatively interposed between said plunger structure and said base wall structure for cushioning the impetus of impacts applied to said plunger buffer plate acting longitudinally of the path of movement thereof,

said cushioning means comprising:

a hydraulic cushioning unit operatively interposed between said plunger structure and said base wall structure for hydraulically cushioning said impacts throughout said stroke length in moving from an extended to a contracted relation,

said hydraulic unit being of the pressure sensitive orifice metering type and comprising:

a hydraulic cylinder carried by one of said structures,

a ram carried by the other of said structures in substantial longitudinal alignment with said cylinder and having a piston head at one end thereof slidably mounted within said cylinder to define hydraulic liquid receiving chambers on opposite sides of said head,

a passage extending through said head to establish communication between said chambers through said head,

hydraulic liquid filling said chambers,

and means for controlling the flow of said hydraulic liquid through said piston head between said chambers under impact forces acting on said buffer plate for cushioning impacts applied to said buffer plate by the passage of the hydraulic liquid between said chambers to permit movement of said ram relative to said cylinder,

said controlling means including pressure responsive valve means operating in said piston head passage for controlling said hydraulic liquid flow between said chambers under instantaneous pressures acting on the high pressure side of said ram head in accordance with a predetermined force travel relationships,

and a tubular flexible sealing member received about said ram and connected at either end of same to said ram and cylinder respective to form a static type hydraulic seal between said ram and said cylinder and define in part the chamber on the lower pressure side of said ram head,

and one or more resilient cushioning units applied to said base wall structure exteriorly of said hydraulic unit and in the path of movement of said plunger structure,

said resilient cushioning units each comprising:

a pad of resiliently compressible material mounted in said housing against abutment means made fast to said housing,

said plunger structure including an abutment member made fast thereto positioned to move toward and away from said resilient cushioning unit as said plunger structure moves along its path of movement and being positioned to engage said pad after a predetermined movement of said plunger structure under an impact toward said base wall structure,

means for making said housing base wall structure fast to the scraper,

and means for biasing said plunger structure outwardly of said housing to return said hydraulic cushioning unit to its extended relation. 

1. A cushioned bumper for scrapers, said bumper comprising: a housing having a base wall at one end of same and having its opposite end open, a tubular plunger structure reciprocably mounted in said housing for movement toward and away from said base wall for a stroke of predetermined length, said base wall being normal to the path of movement of said plunger structure, said plunger structure projection exteriorly of said housing through said open end of said housing and carrying a buffer plate on the projecting end thereof closing said projecting end of same, composite cushioning means operatively interposed between said plunger structure and said base wall for cushioning the impetus of impacts applied to said plunger acting longitudinally of the path of movement thereof, said cushioning means comprising: a hydraulic cushioning unit operatively interposed between said plunger structure and said base wall for hydraulically cushioning said impacts throughout said stroke length in moving from an extended to a contracted relation, said hydraulic unit being of the pressure sensitive orifice metering type and being received within said housing and said plunger structure, and one or more resilient cushioning units applied to said base wall in the path of movement of said plunger structure, a pad of resiliently compressible material mounted in said housing against abutment means made fast to said housing, said plunger structure including an abutment member made fast thereto positioned to move toward and away from said resilient cushioning unit as said plunger structure moves along its path of movement and positioned to engage said pad after a predetermined movement of said plunger structure under an impact toward said base wall, means for making said housing base wall fast to the scraper, and means for biasing said plunger structure outwardly of said housing to return said hydraulic cushioning unit to its extended relation, said housing and said plunger structure being of generally complemental quadrilateral cross-sectional configuration defining opposed side walls on either side of same, with the plunger structure side walls each including a stop lug on the outwardly facing side of same, said housing side walls being respectively slotted longitudinally of said path of movement to receive the respective plunger structure lugs, said housing side walls each having made fast thereto over their said slots a mounting plate including a stop lug disposed in the path of movement of the respective plunger structure lugs to limit movement of said plunger structure outwardly of said housing and define one end of said stroke.
 2. The cushioned bumper set forth in claim 1 wherein: said mounting plates are formed with a venting perforation in alignment with the lower edge of each said slots and adjacent either end of said slots, whereby extraneous material accumulating in said slots is discharged through said venting perforations on cushioning operation of said bumper.
 3. The cushioned bumper set forth in claim 1 wherein: said housing adjacent the base of said base wall is formed with spaced venting perforations, whereby extraneous material accumulating within said housing is discharged through said venting perforations.
 4. The cushioned bumper set forth in claim 1 wherein: said plunger structure engages said base wall to limit movement of said plunger structure inwardly of said housing and defines the other end of said stroke.
 5. The cushioned bumper set forth in claim 1 wherein said resilient cushioning units further each comprise: said pad of said resilient cushioning units being annular in configuratIon, said pad being received on a centering stem made fast to said base wall and extending toward said plunger structure, said pad being seated against said base wall on one side of said pad, and including an annular abutment member on the other side of said pad against which said plunger structure abutment member engages to compress said pad.
 6. The cushioned bumper set forth in claim 1 wherein: said housing and said plunger structure are rectangular in transverse cross-sectional configuration, and wherein said resilient cushioning unit and said plunger structure are in duplicate form on either side of said hydraulic cushioning unit, said hydraulic unit being self contained in nature.
 7. A cushioned bumper for scrapers, said bumper comprising: a housing having a base wall structure at one end of same and having its opposite end open, a tubular plunger structure reciprocably mounted in said housing for movement toward and away from said base wall for a stroke of predetermined length, said base wall being normal to the path of movement of said plunger structure, said plunger structure projecting exteriorly of said housing through said open end of said housing and carrying a buffer plate on the projecting end thereof closing said projecting end of same, composite cushioning means operatively interposed between said plunger structure and said base wall structure for cushioning the impetus of impacts applied to said plunger buffer plate acting longitudinally of the path of movement thereof, said cushioning means comprising: a hydraulic cushioning unit operatively interposed between said plunger structure and said base wall structure for hydraulically cushioning said impacts throughout said stroke length in moving from an extended to a contracted relation, said hydraulic unit being of the pressure sensitive orifice metering type and comprising: a hydraulic cylinder carried by one of said structures, a ram carried by the other of said structures in substantial longitudinal alignment with said cylinder and having a piston head at one end thereof slidably mounted within said cylinder to define hydraulic liquid receiving chambers on opposite sides of said head, a passage extending through said head to establish communication between said chambers through said head, hydraulic liquid filling said chambers, and means for controlling the flow of said hydraulic liquid through said piston head between said chambers under impact forces acting on said buffer plate for cushioning impacts applied to said buffer plate by the passage of the hydraulic liquid between said chambers to permit movement of said ram relative to said cylinder, said controlling means including pressure responsive valve means operating in said piston head passage for controlling said hydraulic liquid flow between said chambers under instantaneous pressures acting on the high pressure side of said ram head in accordance with a predetermined force travel relationships, and a tubular flexible sealing member received about said ram and connected at either end of same to said ram and cylinder respective to form a static type hydraulic seal between said ram and said cylinder and define in part the chamber on the lower pressure side of said ram head, and one or more resilient cushioning units applied to said base wall structure exteriorly of said hydraulic unit and in the path of movement of said plunger structure, said resilient cushioning units each comprising: a pad of resiliently compressible material mounted in said housing against abutment means made fast to said housing, said plunger structure including an abutment member made fast thereto positioned to move toward and away from said resilient cushioning unit as said plunger structure moves along its path of movement and being positioned to engage said pad after a predetermined movement of said plunger structure under an impact toward said base wall Structure, means for making said housing base wall structure fast to the scraper, and means for biasing said plunger structure outwardly of said housing to return said hydraulic cushioning unit to its extended relation. 